Modeling an arc

I would like to ask some help in modeling again. Because I have earlier been using Google Sketchup, there are some very basic things that I have hard times to learn in Blender. This is mainly because the logic needs to be totally different when modeling with Blender.

How would you model this kind of arc in Blender, see picture? I would need to draw an arc that has end points in the corners of rectangular. Also, how would you do it in both Object mode (arc would be separate object) and edit mode?

Is there some addon available that could be useful?

the easiest way would be to add a circle, delete some of the bottom vertexes, then extrude downward from the remaining ones.

also depends on windows type
some medieval window required parabola style curve!

and there is somewhere a script to make windows like that !

happy bl


  • Started with a plane
  • Loop cut in the middle (ctrl+R, cancel slide)
  • Selected middle vertex and snapped cursor to it (shift+S -> cursor to selected) and then selected leftmost vertex and used spin (alt+R)
  • Adjusted values from the operator panel (arrow), selected all, W -> remove doubles
  • Fills (F) and inset (i)


  • Again started with a plane
  • Snap and spin, removed doubles
  • Moved top vertex down with proportional edit in connected mode (alt+O, root falloff)
  • Fills, inset

Bezier curve with mirror modifier is my way.


Thanks for all the tips, learning everyday something new :)!

Also Bevel Modifier:

Had the same problem. Thanks a lot for this very nice explanation! Helped me a lot!

edit: Played a little bit more with it and wanted to bould something 3D, but If I try I get confused with the spin coordinates. It is not making this 90° along X and Z axis, it is turning into the X axis as well. Will play a little bit more with it. But very handy.

Spin is view and 3D cursor dependent. I did those in the top orthographic view so it aligns perfectly. Could also set the axis from the operator panel after spinning.

Thanks for the tip. I will give it a try!

Did someone hear the bell by the headstone!